1. Field of the Invention
The present invention relates to a holding apparatus of r holding an object such as an electric component (e.g., an electronic component), a transferring apparatus including the holding apparatus, and an image taking system and an image taking method each for taking an image of an object held by a holding device, and relates particularly to the art of lighting an object.
2. Related Art Statement
The above-indicated holding apparatus , a transferring apparatus, an image taking system, and an image taking method are employed by, e.g. , an electric-component mounting system which mounts an electric component on a printed circuit board (xe2x80x9cPCBxe2x80x9d). In the electric-component mounting system, the holding apparatus receives an electric component from an electric-component supplying device and mounts the component at a predetermined position on the PCB. Even if the current X-direction and Y-direction positions of the component held by the holding apparatus are deviated from respective reference positions, the component can be accurately mounted at the predetermined position on the PCB, by moving the holding apparatus to a corrected or modified position deviated from the predetermined position by respective distances between the X-direction and Y-direction positions of the component and the corresponding reference positions. To this end, it is needed to measure the respective distances between the X-direction and Y-direction positions of the component held by the holding apparatus and the corresponding reference positions. In addition, in some cases, it is needed to read characters and/or a bar code affixed to the component and judge of what sort the component is based on the read characters and/or bar code. To these ends, it is widely practiced that an image taking device takes an image of the component. Depending upon respective shapes of different sorts of electric components and/or different purposes of image taking, a silhouette image of each component is preferably needed in some cases, and a front-surface image of each component is preferably needed in other cases. To take a silhouette image of an electric component held by the holding apparatus, it is needed to light a back surface of the component that is held by the holding apparatus. To take a front-surface image of the component held by the holding apparatus, it is needed to light a front surface of the component that is opposed to the image taking device.
There is a holding apparatus which includes a suction nozzle for sucking and holding an electric component; a front-surface lighting device which lights a front surface of the component held by the nozzle; and a back-surface lighting device which lights a back surface of the component. With this holding apparatus, an image taking device can selectively take a silhouette image or a front-surface image of the component. Thus, the holding apparatus can be widely used. However, the light emitting surface of the back-surface lighting device is considerably light and, if the image taking device takes a front-surface image of the component in the background defined by the light emitting surface while the front-surface lighting device lights the front surface of the component, the image taking device takes, in addition to the front-surface image of the component, a light image of the background. In this case, it is difficult to extract accurately the image of the object from the background, and incorrect results may be obtained by the processing of the extracted image of the object. This problem might be solved by moving the back-surface lighting device away from the object when the front-surface image of the object is taken. In the latter case, however, the holding apparatus needs a more complicated structure, which leads to another problem that the production cost of the holding apparatus increases. In a particular case where the taking of front-surface image and the taking of silhouette image are frequently switched with each other, it needs a long time to switch them, which leads to lowering the operating efficiency of the holding apparatus.
In addition, it has widely been practiced that the suction nozzle and a main portion of the back-surface lighting device are constructed as an integral unit. For example, a light emitting plate including a plurality of point light sources, such as light emitting diodes, and a diffusing layer for diffusing the lights emitted by the point light sources and thereby emitting a substantially uniform light, is fixed to the suction nozzle, or alternatively a light emitting plate which absorbs infrared rays externally incident thereto and emits a visible light, a reflecting plate which reflects a light externally incident thereto, or a diffusing block which diffuses a light externally incident thereto and emits a light toward the suction nozzle, is fixed to the suction nozzle.
However, if the main portion of the back-surface lighting device is provided as the integral portion of the suction nozzle, the suction nozzle costs high. Generally, the suction nozzle includes a suction pipe, which may be bent to be not usable or whose suction surface (i.e., free end surface) may be worn to be not usable. If the main portion of the back-surface lighting device is provided as the integral portion of the suction nozzle, the suction nozzle as a whole including the main portion of the back-surface lighting device must be replaced with another suction nozzle including a main portion of another back-surface lighting device. This manner leads to increasing the running cost of the electric-component mounting system. Meanwhile, in the case where a plurality of sorts of suction nozzles are exchanged with one another corresponding to a plurality of sorts of electric components to be held, the number of suction nozzles employed increases. If each of those suction nozzles includes a main portion of a back-surface lighting device, the running cost costs very high. Moreover, in the case where the main portion of each back-surface lighting device includes a light emitting source, the light emitting source must be supplied with electric power. In the last case, when the suction nozzles are repetitively exchanged with one another, the contact of an electric-power supply circuit which supplies the electric power to the light emitting source may be worn or damaged, or an electric noise may be produced from the contact.
While the foregoing explanation relates to the holding apparatus, the transferring apparatus, the image taking device, etc. which are for use with electric components, objects to be held by the holding apparatus are not limited to the electric components. The above-explained problems may commonly occur to all holding apparatuses, all transferring apparatuses, all image taking devices, etc. that are for use with objects whose images need to be taken to recognize each object by image processing or to determine X-direction, Y-direction, and rotation positions of each object, measure one or more dimensions of each object, etc.
The present invention provides a holding apparatus, a transferring apparatus, an image taking system, and an image taking method that have one or more of the technical features that are described below in respective paragraphs given parenthesized sequential numbers (1) to (15). Any technical feature which includes another technical feature shall do so by referring, at the beginning, to the parenthesized sequential number given to that technical feature. Thus, two or more of the following technical features may be combined, if appropriate. Each technical feature may be accompanied by a supplemental explanation, as needed. However, the following technical features and the combinations thereof are just examples to which the present invention is by no means limited.
(1) According to a first feature of the present invention, there is provided a holding apparatus comprising a suction nozzle which applies a negative pressure to a back surface of an object and thereby holds the object; a front-surface lighting device which emits a first visible light toward a front surface of the object held by the suction nozzle and thereby lights the front surface; and a back-surface lighting device which lights the back surface of the object held by the suction nozzle and which includes (a) a light emitting plate which is provided around a base portion of the suction nozzle and emits a second light from a light emitting surface thereof facing a side of a free end of the suction nozzle that holds the object; and (b) a dark infrared-ray transmitting filter which is dark, covers the light emitting surface of the light emitting plate, and transmits infrared rays of the second light. The dark infrared-ray transmitting filter may be black. In the present holding apparatus, the light emitting surface of the light emitting plate of the back-surface lighting device is covered by the dark infrared-ray transmitting filter. Accordingly, when the front-surface lighting device lights the front surface of the object in taking a front-surface image of the object, the background of the object is defined by the dark filter. If the background is light, an image taking device takes, in addition to the front-surface image of the object, a light image of the background, so that when the taken images are processed, it is difficult to extract accurately the image of the object from that of the background. Since the present holding apparatus provides the dark background, the image of the object can be accurately extracted from that of the background. Meanwhile, when a silhouette image of the object is taken, the light emitting plate of the back-surface lighting device emits a light and the infrared-ray transmitting filter absorbs a visible-ray component of the emitted light and transmits infrared rays only. Therefore, with an image taking device which is sensitive to the infrared rays, a silhouette image of the object can be taken. Accordingly, the present holding apparatus allows a user or an operator to obtain selectively a silhouette image or a front-surface image of the object by just operating selectively the back-surface lighting device or the front-surface lighting device. Thus, the present holding apparatus enjoys much ease of use. In the case where an image taking device which is sensitive to both the visible light and the infrared rays is employed, the single image taking device can be commonly used to take both the silhouette and front-surface images of the object. This feature contributes to reducing the production cost of the holding apparatus.
(2) According to a second feature of the present invention that includes the first feature (1), the light emitting plate comprises a plurality of light emitting elements arranged along the light emitting surface thereof, and a diffusing plate which covers the light emitting surface and which diffuses respective lights emitted by the light emitting elements and thereby emits a substantially uniform light. If a plurality of light emitting elements are arranged along a plane, a light emitting plate can be obtained which has a light emitting surface defined by the plane. In this case, however, the distribution of light along the light emitting plane cannot be uniform. In the present holding apparatus, the light emitting plate is covered by the diffusing plate which diffuses the light emitted by the light emitting surface, thereby reducing the uneven distribution of light and emitting a substantially uniform light. The diffusing plate and the infrared-ray transmitting filter may be provided by respective layers which are superposed on each other, or may be provided by a single layer which functions as both of them.
(3) According to a third feature of the present invention that includes the first or second feature (1) or (2), the holding apparatus further comprises a support portion to which the suction nozzle is detachably attached, the back-surface lighting device including a main portion which is separate from the suction nozzle and is supported by the support portion such that when the suction nozzle is detached from the support portion, the main portion remains supported by the support portion. In the present holding apparatus, the suction nozzle can be detached, as needed, from the support portion, while the main portion of the back-surface lighting device remains supported by the support portion. For example, in the case where a plurality of sorts of suction nozzles are exchanged with one another corresponding to a plurality of sorts of objects to be held, the main portion of the single back-surface lighting device may be commonly used with each selected one of the different sorts of suction nozzles. This feature also contributes to decreasing the running cost of the holding apparatus. Moreover, even in the case where the main portion of the back-surface lighting device includes a light emitting source, the main portion need not be detached from the support portion when the different sorts of suction nozzles are exchanged with one another. This feature solves the problems that the contact of an electric-power supply circuit is worn or damaged and an electric noise is produced from the contact. According to the present invention, a portion of the back-surface lighting device may be provided as an integral portion of the suction nozzle or each of the different sorts of suction nozzles. In this case, the suction nozzle, or each suction nozzle, including the portion of back-surface lighting device is attached to, and detached from, the support portion of the holding head. Alternatively, the entirety of the back-surface lighting device may be directly supported by the support portion of the holding apparatus. In the last case, when the suction nozzle is detached from the support portion, no portion of the back-surface lighting device is detached from the support portion.
(4) According to a fourth feature of the present invention that includes the third feature (3), the main portion of the back-surface lighting device comprises a tubular lighting portion which emits, from an inner surface thereof, a first light; and an outer lighting portion which extends outward from the tubular lighting portion and which emits, from one surface thereof, a second light in a direction parallel to a centerline of the tubular lighting portion, and wherein the suction nozzle comprises a light converting portion which is fitable in an inner space of the tubular lighting portion and which converts the first light emitted by the tubular lighting portion into a third light having the direction parallel to the centerline of the tubular lighting portion; and a suction pipe which holds the object and which extends from one end of the light converting portion in the direction parallel to the centerline of the tubular lighting portion, one end portion of the suction nozzle that is opposite to the suction pipe being detachably attached to the support portion. In the present holding apparatus, the suction nozzle includes, in addition to the suction pipe, the light converting portion as a portion of the back-surface lighting device. In the state in which the suction nozzle is attached to the support portion of the holding apparatus, the light converting portion is positioned in the inner space of the tubular lighting portion, and converts the light emitted from the inner surface of the tubular lighting portion into a light having a direction parallel to the centerline of the tubular lighting portion. Thus, the back surface of the object held by the suction pipe is lighted with a sufficient amount of light even in the vicinity of the pipe, and a clear silhouette image of the object can be taken by an image taking device. It is preferred that the inner surface of the tubular lighting portion has a circular cross section. However, the inner surface may have a square cross section or any other appropriate shape. The fourth feature (4) may not be combined with the third feature (3) wherein the suction nozzle can be detached from the support portion while the main portion of the back-surface lighting device still remains supported by the support portion. That is, a holding apparatus may employ the fourth feature (4), independent of the third feature (3).
(5) According to a fifth feature of the present invention that includes the fourth feature (4), at least one of the tubular lighting portion and the outer lighting portion comprises a plurality of light emitting elements which emits respective lights and which are arranged on a plurality of lattice points, respectively; and a diffusing layer which diffuses the lights emitted by the light emitting elements and thereby emits a substantially uniform light. In the present holding apparatus, the light emitting elements need the supply of electric power. However, the light emitting elements can remain on the support portion when the suction nozzle is detached from the support portion. Therefore, an electric-power supply circuit which supplies the electric power to the light emitting elements need not be provided with a contact that is frequently connected and disconnected. Thus, the present holding apparatus is free of the problems that the contact is damaged and an electric noise is produced from the contact.
(6) According to a sixth feature of the present invention that includes the fourth or fifth feature (4) or (5), the light converting portion comprises a tapered reflecting surface which is coaxial with the suction pipe and whose radius increases in a direction away from a free end of the suction pipe that holds the object. The tapered reflecting surface can easily deflect the light emitted radially inward from a cylindrical inner circumferential surface of the tubular lighting portion, to a direction substantially parallel to an axis line of the suction pipe.
(7) According to a seventh feature of the present invention that includes the fourth or fifth feature (4) or (5), the light converting portion comprises a diffusing block which diffuses the first light emitted by the tubular lighting portion and emits the third light from an outer surface thereof located on a side of the suction pipe. The diffusing block receives, at the outer surface thereof, the light emitted from the inner surface of the tubular lighting portion, and diffuses therein the received light so that the block becomes lighter as a whole. Accordingly, a light is emitted toward the object held by the suction pipe from a pipe-side surface of the diffusing block.
(8) According to an eighth feature of the present invention that includes any one of the fourth to seventh features (4) to (7), the holding apparatus further comprises a support rod which is supported by the support portion such that the support rod is movable in a direction parallel to an axis line of the suction pipe; an attaching device which attaches the suction nozzle to one end portion of the support rod such that the suction nozzle is detachable from the support rod; and a support-rod moving device which moves the support rod in a direction parallel to an axis line thereof, thereby moving the light converting portion of the suction nozzle relative to the tubular lighting portion in the direction parallel to the centerline thereof, so that the suction pipe of the suction nozzle is advanceable and retractable in the direction parallel to the axis line thereof. In the present holding apparatus, the suction nozzle including the light converting portion and the suction pipe is attached to the support portion via the support rod, and the support rod is moved, by the support rod moving device, relative to the support portion in an axial direction of the rod, so that the suction pipe is advanced and retracted in an axial direction thereof. The advancing and retracting movements of the suction pipe can be utilized for, e.g., causing the pipe to hold the object or mount the object on a mount surface. For example, in the case where the object is an electric component, the suction pipe can be caused to take the component from an electric-component supplying device and mount the same on a PCB. In this case, since the main portion of the back-surface lighting device need not be advanced or retracted with the suction nozzle, the nozzle can be quickly advanced and retracted while being prevented from producing vibration or noise. Thus, the present holding apparatus can mount electric components with high efficiency. In addition, the main portion of the back-surface lighting device can be effectively prevented from interfering with electric components which have already been mounted on the PCB, and the force with which the suction nozzle contacts each electric component and/or the force with which the nozzle presses each component on the PCB can be accurately controlled.
(9) According to a ninth feature of the present invention that includes any one of the fourth to eighth features (4) to (8), the main portion of the back-surface lighting device further comprises an auxiliary lighting portion which is opposed to a gap provided between the tubular lighting portion and the light converting portion and which emits a fourth light toward a side of the suction pipe via the gap. In the present holding apparatus, the auxiliary lighting portion lights the gap provided between the tubular lighting portion and the outer lighting portion. Accordingly, the back surface of the object is lighted with a uniform light and a clear silhouette image of the object can be obtained.
(10) According to a tenth feature of the present invention, there is provided a transferring apparatus comprising a holding apparatus according to any one of the first to ninth features (1) to (9); a moving device which moves the suction nozzle and the back-surface lighting device of the holding apparatus in a direction perpendicular to an axis line of the suction nozzle; and an image taking device which is provided at a predetermined position in a range in which the moving device moves the suction nozzle and the back-surface lighting device of the holding apparatus, so that when the suction nozzle and the back-surface lighting device are positioned at the predetermined position, the image taking device is opposed to the suction nozzle and the back-surface lighting device and takes an image of the object held by the suction nozzle. The range in which the holding apparatus is moved may be a one-dimensional, two-dimensional, or three-dimensional range. In the present transferring apparatus, the object is held by the holding apparatus, which in turn is moved by the moving device, so that the holding apparatus is opposed to the image taking device. Thus, a silhouette image of the object held by the suction nozzle can be taken by the image taking device. Image data representing the thus taken silhouette image may be processed to identify the object, determine one or more positions of the object held by the suction nozzle, and/or measure one or more dimensions of the object. For example, in the case where the object is an electric component, the holding apparatus receives the electric component from an electric-component supplying device, transfers it, and mounts it on a PCB. Before the holding apparatus mounts the component on the PCB, the image taking device takes an image of the component held by the suction nozzle, and the taken image is processed to determine one or more sorts of positional errors of the component held by the nozzle. After the positional errors of the component are corrected, the holding apparatus mounts the component on the PCB.
(11) According to an eleventh feature of the present invention that includes the tenth feature (10), the transferring apparatus further comprises a nozzle stocker which stocks at least one suction nozzle; and a nozzle-exchange control device which controls the moving device to move the suction nozzle of the holding apparatus to a position where the suction nozzle of the holding apparatus is opposed to the nozzle stocker, and causes the suction nozzle of the holding apparatus to be exchanged with the one suction nozzle stocked by the nozzle stocker. In the present transferring apparatus, the moving device for transferring the object held by the suction nozzle is additionally used for automatically exchanging the suction nozzles with each other. Thus, the transferring apparatus capable of automatically exchanging the suction nozzles can be produced at low cost.
(12) According to a twelfth feature of the present invention, there is provided an image taking system comprising a front-surface lighting device which emits a first visible light toward a front surface of an object whose back surface is held by a holding portion of a holding device and thereby lights the front surface; a first image taking device which is sensitive to the first visible light and takes an image of the object being lighted by the front-surface lighting device; a back-surface lighting device which is provided in back of the object held by the holding portion of the holding device, which lights the back surface of the object held by the holding portion, and which includes (a) a light emitting plate which emits a second light from a light emitting surface thereof facing a side of the holding portion holding the back surface of the object; and (b) a dark infrared-ray transmitting filter which is dark, covers the light emitting surface of the light emitting plate, and transmits infrared rays of the second light; and a second image taking device which is sensitive to the infrared rays and takes an image of the object being lighted by the back-surface lighting device. The present image taking system can take an excellent silhouette image of the object while the back-surface lighting device lights with the infrared rays the back surface of the object, and can take an easily processable front-surface image of the object in a dark background defined by the infrared-ray transmitting filter of the back-surface lighting device. Thus, the present image taking system can selectively take, with ease, an excellent silhouette image and an excellent front-surface image of the object.
(13) According to a thirteenth feature of the present invention that includes the twelfth feature (12), the first and second image taking devices is provided by a single image taking device which is sensitive to both the first visible light and the infrared rays of the second light. In the present image taking system, the single image taking device can be commonly used to take a silhouette image formed by the infrared rays and take a front-surface image formed by the visible light. This feature contributes to reducing the production cost of the image taking system.
(14) According to a fourteenth feature of the present invention, there is provided a method of taking an image of an object which is held by a holding device, comprising the steps of providing, in front of the object whose back surface is held by a holding portion of the holding device, a front-surface lighting device which emits a first visible light toward a front surface of the object and thereby lights the front surface, providing, in back of the object held by the holding portion of the holding device, a back-surface lighting device which lights the back surface of the object held by the holding portion and which includes (a) a light emitting plate which emits a second light from a light emitting surface thereof facing a side of the holding portion holding the back surface of the object; and (b) a dark infrared-ray transmitting filter which is dark, covers the light emitting surface of the light emitting plate, and transmits infrared rays of the second light, operating the front-surface lighting device and a first image taking device which is sensitive to the first visible light, to take, in a background defined by the dark infrared-ray transmitting filter, an image of the front surface of the object that is lighted by the front-surface lighting device, and operating the back-surface lighting device and a second image taking device which is sensitive to the infrared rays of the second light, to take a silhouette image of the object whose back surface is lighted by the back-surface lighting device. The present image taking method can enjoy the same advantages as those of the image taking system according to the twelfth feature (12).
(15) According to a fifteenth feature of the present invention that includes the fourteenth feature (14), the first and second image taking devices is provided by a single image taking device which is sensitive to both the first visible light and the infrared rays of the second light. The present image taking method can enjoy the same advantages as those of the image taking system according to the thirteenth feature (13).